Well cement compositions comprising biowaste ash and methods of use

ABSTRACT

Cement compositions containing biowaste ash and methods of cementing in subterranean formations using such cement compositions. Examples of suitable biowaste ash include agricultural waste ash, municipal waste ash, waste-water treatment waste ash, animal waste ash, non-human-non-animal industrial waste ash, and combinations thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 12/497,402, entitled “Well Cement Compositions Comprising BiowasteAsh and Methods of Use,” filed on Jul. 2, 2009, the entire disclosure ofwhich is incorporated herein by reference.

BACKGROUND

The present invention relates to cementing operations and, moreparticularly, in certain embodiments, to cementing methods andcompositions that comprise biowaste ash.

Cement compositions may be used in a variety of subterraneanapplications. For example, in subterranean well construction, a pipestring (e.g., casing, liners, expandable tubulars, etc.) may be run intoa well bore and cemented in place. The process of cementing the pipestring in place is commonly referred to as “primary cementing.” In atypical primary cementing method, a cement composition may be pumpedinto an annulus between the walls of the well bore and the exteriorsurface of the pipe string disposed therein. The cement composition mayset in the annular space, thereby forming an annular sheath of hardened,substantially impermeable cement (i.e., a cement sheath) that maysupport and position the pipe string in the well bore and may bond theexterior surface of the pipe string to the subterranean formation. Amongother things, the cement sheath surrounding the pipe string functions toprevent the migration of fluids in the annulus, as well as protectingthe pipe string from corrosion. Cement compositions also may be used inremedial cementing methods, for example, to seal cracks or holes in pipestrings or cement sheaths, to seal highly permeable formation zones orfractures, to place a cement plug, and the like.

Cement compositions used heretofore commonly comprise Portland cement,which is generally is a major component of the cost for the cementcompositions. To reduce the cost of such cement compositions, othercomponents may be included in the cement composition in addition to, orin place of, the Portland cement. Such components may include fly ash,slag cement, shale, metakaolin, micro-fine cement, cement kiln dust,zeolite, and the like. “Fly ash,” as that term is used herein, refers tothe residue from the combustion of powdered or ground coal, wherein thefly ash carried by the flue gases may be recovered, for example, byelectrostatic precipitation. “Slag,” as that term is used herein, refersto a granulated, blast furnace by-product formed in the production ofcast iron and generally comprises the oxidized impurities found in ironore. Slag cement generally comprises slag and a base, for example, suchas sodium hydroxide, sodium bicarbonate, sodium carbonate, or lime, toproduce a cement composition that, when combined with water, may set toform a hardened mass.

Large amounts of biowaste are generated worldwide each year. Biowasteash can be derived from a number of sources including agriculturalwaste, municipal waste, waste-water treatment waste, animal waste,non-human-non-animal industrial waste, and combinations thereof. Anumber of different methods for disposal of biowaste have beendeveloped, including application to surface land, composting, andlandfill disposal. In addition, billions of tons of biowaste are burntevery year, resulting in tons of ashes that must be disposed.

SUMMARY

The present invention relates to cementing operations and, moreparticularly, in certain embodiments, to cementing methods andcompositions that comprise biowaste ash.

An embodiment of the present invention provides a method of cementing.The method may comprise introducing a cement composition into asubterranean formation, wherein the cement composition may comprisehydraulic cement, water, and biowaste ash. The method further maycomprise allowing the cement composition to set in the subterraneanformation.

Another embodiment of the present invention provides a method ofcementing. The method may comprise introducing a cement composition intoa subterranean formation, wherein the cement composition compriseshydraulic cement, water, biowaste ash, and at least one additiveselected from the group consisting of cement kiln dust, fly ash, anatural pozzalon, metakaolin, shale, slag, zeolite, and combinationsthereof. The method further may comprise allowing the cement compositionto set in the subterranean formation.

Another embodiment of the present invention provides a subterraneanformation cementing composition that may comprise hydraulic cement,water, biowaste ash, and at least one additive selected from the groupconsisting of a strength-retrogression additive, a set accelerator, aset retarder, a weighting agent, a lightweight additive, agas-generating additive, a mechanical-property-enhancing additive, alost-circulation material, a filtration-control additive, a dispersant,a fluid loss control additive, a defoaming agent, a foaming agent, athixotropic additive, an oil-swellable material, a water-swellablematerial, and combinations thereof.

The features and advantages of the present invention will be readilyapparent to those skilled in the art. While numerous changes may be madeby those skilled in the art, such changes are within the spirit of theinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to cementing operations and, moreparticularly, in certain embodiments, to cementing methods andcompositions that comprise biowaste ash.

There may be several potential advantages to the methods andcompositions of the present invention, only some of which may be alludedto herein. One of the many potential advantages of the methods andcompositions of the present invention may be that the inclusion of thebiowaste ash in embodiments of the cement compositions may reduce theamount of a higher cost additive, such as Portland cement, resulting ina more economical cement composition. Another potential advantage of themethods and compositions of the present invention may be that inclusionof the biowaste ash in embodiments of the cement compositions providesan additional method for the disposal of biowaste. Yet another potentialadvantage of the methods and compositions of the present invention maybe that inclusion of the biowaste ash in embodiments of the cementcompositions may enhance mechanical properties of the cementcompositions, including, for example, compressive strength.

An embodiment of the cement compositions of the present inventioncomprises hydraulic cement, water, and biowaste ash. The cementcompositions optionally may comprise a number of additional components,including cement kiln dust (“CKD”), fly ash, a natural pozzolan,metakaolin, shale, slag, zeolite, and combinations thereof. In certainembodiments, the cement compositions may be foamed with a gas.Embodiments of the present invention also include methods of cementingthat comprise: introducing the cement composition into a subterraneanformation; and allowing the cement composition to set in thesubterranean formation.

Those of ordinary skill in the art will appreciate that embodiments ofthe cement compositions generally should have a density suitable for aparticular application. By way of example, embodiments of the cementcompositions may have a density of about 4 pounds per gallon (“lb/gal”)to about 20 lb/gal. In certain embodiments, the cement compositions mayhave a density of about 8 lb/gal to about 17 lb/gal. In certainembodiments, the cement composition may be a lightweight cementcomposition having a density of less than or equal to about 13 lb/gal.In other embodiments, the cement compositions may be foamed and have adensity of about 4 lb/gal to about 13 lb/gal. Embodiments of the cementcompositions may be foamed or unfoamed or may comprise other means toreduce their densities, such as a lightweight additive. Lightweightadditives are generally additives that may be included in a cementcomposition to reduce its density below about 13 lb/gal and may include,for example, bentonite, gilsonite, expanded perlite, and microspheres(e.g., glass spheres). Those of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate density for aparticular application.

Hydraulic cement is a component that may be included in embodiments ofthe cement compositions of the present invention. Any of a variety ofhydraulic cements suitable for use in subterranean cementing operationsmay be used in accordance with embodiments of the present invention.Suitable examples include hydraulic cements that comprise calcium,aluminum, silicon, oxygen and/or sulfur, which set and harden byreaction with water. Such hydraulic cements, include, but are notlimited to, Portland cements, pozzolana cements, gypsum cements,high-alumina-content cements, slag cements, silica cements andcombinations thereof. In certain embodiments, the hydraulic cement maycomprise a Portland cement. The Portland cements that may be suited foruse in embodiments of the present invention are classified as Class A,C, G and H cements according to American Petroleum Institute, APISpecification for Materials and Testing for Well Cements, APISpecification 10, Fifth Ed., Jul. 1, 1990. In addition, in someembodiments, hydraulic cements suitable for use in the present inventionmay include cements classified as ASTM Type I, II, or III.

Where present, the hydraulic cement generally may be included inembodiments of the cement compositions in an amount sufficient toprovide, for example, the desired compressive strength, density, and/orcost. In some embodiments, the hydraulic cement may be present in thecement compositions of the present invention in an amount of about 0.01%to about 99% by weight of cementitious components (“bwoc”). In someembodiments, the hydraulic cement may be present in the cementcompositions of the present invention in an amount of about 1% to about95% bwoc. In some embodiments, the hydraulic cement may be present inthe cement compositions of the present invention in an amount of about1% to about 75% bwoc. In some embodiments, the hydraulic cement may bepresent in the cement compositions of the present invention in an amountof about 1% to about 50% bwoc.

An example of a suitable hydraulic cement comprises a pozzolana cement.In some embodiments, a pozzolana cement that may be suitable for usecomprises fly ash. A variety of fly ashes may be suitable, including flyash classified as Class C and Class F fly ash according to AmericanPetroleum Institute, API Specification for Materials and Testing forWell Cements, API Specification 10, Fifth Ed., Jul. 1, 1990. In someembodiments, lime may be mixed with the fly ash (e.g., Class F fly ash)in an amount of about 0.1% to about 25% by weight of the fly ash. Insome instances, the lime may be hydrated lime (calcium hydroxide).Suitable examples of fly ash include, but are not limited to, POZMIX® Acement additive, available from Halliburton Energy Services, Inc.,Duncan, Okla. Where present, the fly ash generally may be included inembodiments of the cement compositions in an amount sufficient toprovide, for example, the desired compressive strength, density, and/orcost. In some embodiments, the fly ash may be present the cementcompositions of the present invention in an amount of about 0.1% toabout 75% bwoc. In some embodiments, the fly ash may be present in thecement compositions of the present invention in an amount 1% to about50% bwoc.

Another example of a suitable hydraulic cement comprises a slag cement.In some embodiments, a slag cement that may be suitable for use maycomprise slag. Slag generally does not contain sufficient basicmaterial, so slag cement further may comprise a base to produce a cementcomposition that may react with water to set to form a hardened mass.Examples of suitable sources of bases include, but are not limited to,sodium hydroxide, sodium bicarbonate, sodium carbonate, lime, andcombinations thereof. Where present, the slag cement generally may beincluded in embodiments of the cement compositions in an amountsufficient to provide, for example, the desired compressive strength,density, and/or cost. In some embodiments, the slag cement may bepresent in the cement compositions of the present invention in an amount0.01% to about 99% bwoc. In some embodiments, the slag cement may bepresent in the cement compositions of the present invention in an amountof about 1% to about 75% bwoc.

The water used in embodiments of the cement compositions of the presentinvention may include, for example, freshwater, saltwater (e.g., watercontaining one or more salts dissolved therein), brine (e.g., saturatedsaltwater produced from subterranean formations), seawater, orcombinations thereof. Generally, the water may be from any source,provided, for example, that it does not contain an excess of compoundsthat may undesirably affect other components in the cement composition.In some embodiments, the water may be included in an amount sufficientto form a pumpable slurry. In some embodiments, the water may beincluded in the cement compositions of the present invention in anamount of about 40% to about 200% bwoc. In some embodiments, the watermay be included in an amount of about 40% to about 150% bwoc.

Biowaste ash is another component that may be included in embodiments ofthe cement compositions of the present invention. Biowaste ash isgenerally biowaste that has been burned to produce ash and includesplant- and/or animal-derived waste products. Biowaste ash, as definedherein, does not include fly ash or rice hull ash. As previouslydescribed, the biowaste and/or biowaste ash is often disposed of as awaste, but may include any ash that is specifically produced from thesources described herein for use in the various embodiments of theinvention. However, in accordance with embodiments of the presentinvention, the biowaste ash may be used in cementing methods andcompositions. In certain embodiments, the ashes produced from theburning of biowaste can be used as a filler material in cementingapplications. By way of example, the biowaste may be used to replacehigher cost cementitious components, such as Portland cement, resultingin more economical cement compositions. In addition, biowaste ashes cancontain large amounts of silica which can form the basis of a pozzolanreaction, for example, the reaction of silica oxides with calciumhydroxide during the hydration process. The biowaste ash may react, forexample, with excess hydrated lime present in the cement compositionduring hydration. In addition, hydrated lime may be added to the cementcomposition, for example, to provide sufficient calcium ions for thebiowaste ash to set.

Any biowaste that can be burned to produce ash that may be useful incementing may be suitable for use in embodiments of the presentinvention. Examples of suitable biowaste ash that may be suitable foruse include, for example, agricultural waste ash, municipal waste ash,waste-water treatment waste ash, animal waste ash, non-human-non-animalindustrial waste ash, and combinations thereof. The agricultural wasteash, municipal waste ash and industrial waste ash may also include ashthat is derived from agricultural, municipal or industrial materialsthat have viable other uses and are not necessarily considered to be awaste products. The biowaste ash may also be generated, for example, asa byproduct of combustion for heat and/or power generation. Examples ofagricultural waste ash that may be used in embodiments of the presentinvention include, for example, wood (e.g., sawdust, bark, twigs,branches, other waste wood) ash, tree leave ash, corn cob ash, cane(e.g., sugar cane) ash, bagasse ash, grain (e.g., amaranth, barley, cornflaxseed, millet, oat, quinoa, rye, wheat etc.) and relatedby-product(s) (e.g., husks, hulls, etc.) ash, orchard ash, vine trimmingash, grass (e.g., Korai, Tifton, native shiba, etc.) ash, straw ash,ground nut shell ash, legume (e.g., soybean) ash, and combinationsthereof. As defined herein, “agricultural waste ash” and “grain relatedby-product ash” do not include rice hull ash. Municipal waste ashes thatmay be useful in embodiments of the present invention include municipalsolid waste ashes and municipal sewage waste ashes, including, forexample, human biowaste ash, food waste ash, household scrap ash,sanitary paper product ash, and ashes of other biological components.Municipal sewage waste also may comprise mineral matter and smallamounts of chemical products that can be introduced, for example, intothe waste stream through a municipal sewer system. Animal waste ashesthat may be used in embodiments of the present invention include, forexample, ashes derived from burning manure and other animal wastes thatmay be generated at sites where animals are raised or housed. Otherbiowaste ashes, such as non-human-non-animal industrial waste ashes,that may be used in embodiments of the present invention include, forexample, ashes derived from pulp and paper mill sludges, waste oilproducts including greases and solids, and wastes that include organicdebris dredged from harbors or estuaries.

Burn duration and burn temperature, for example, may impact thecomposition of the ash obtained from the biowaste. The burn temperature,as used herein, refers to the temperature at which the biowaste isexposed during the burning and not to the temperature of the biowasteitself. It should be understood that the biowaste may be burned at awide variety of times and temperatures to produce ash suitable for usein embodiments of the present invention. By way of example, the biowastemay be burned for about 2 hours to about 8 hours and, alternatively, forabout 3 hours to about 6 hours. In certain embodiments, the biowaste maybe burned for about 5 hours. By way of further example, the ash may beburned at a temperature of about 400° C. to about 900° C. and,alternatively, of about 500° C. to about 700° C. In certain embodiments,the ash may be burned at a temperature of about 600° C. It should beunderstand that burn times and burn temperatures outside those listed inthis disclosure may also be suitable for embodiments of the presentinvention.

In general, the biowaste ash may be included in embodiments of thecement compositions in an amount sufficient for a particularapplication. In some embodiments, the biowaste ash may be present in anamount of about 0.1% to about 75% bwoc. In some embodiments, thebiowaste ash may be present in an amount about 1% to about 50% bwoc. Insome embodiments, the biowaste ash may be present in an amount about 1%to about 25% bwoc.

As previously mentioned, embodiments of the cement compositions of thepresent invention may further comprise CKD, fly ash, a natural pozzolan,metakaolin, shale, slag, zeolite, and combinations thereof. In addition,hydrated lime may also be included in embodiments of the cementcompositions. Each of these additional additives will be described inmore detail in the following paragraphs.

CKD may be included in embodiments of the cement compositions of thepresent invention. Where present, the CKD may be included in the cementcompositions in an amount sufficient to provide, for example, thedesired compressive strength, density, and/or cost reduction. In someembodiments, the CKD may be present in the cement compositions of thepresent invention in an amount of about 0.1% to about 99% bwoc. In someembodiments, the CKD may be present in the cement compositions of thepresent invention in an amount of about 1% to about 50% bwoc. One ofordinary skill in the art, with the benefit of this disclosure, willrecognize the appropriate amount of the CKD to include for a chosenapplication.

A natural pozzolan may be included in embodiments of the cementcompositions of the present invention. Natural pozzolans are generallypresent on the Earth's surface and should set and harden in the presenceof hydrated lime and water. Examples of natural pozzolans includepumicite, diatomaceous earth, volcanic ash, opaline shale, tuff, andcombinations thereof. Generally, pumicite is a volcanic rock thatexhibits cementitious properties, in that it may set and harden in thepresence of hydrated lime and water. Hydrated lime may be used incombination with pumicite, for example, to provide sufficient calciumions for pumicite to set. The natural pozzolan may be used, among otherthings, to replace higher cost cementitious components, such as Portlandcement, in embodiments of the cement compositions, resulting in moreeconomical cement compositions. In some embodiments, the naturalpozzolan may be present in an amount of about 0.1% to about 50% bwoc. Insome embodiments, the natural pozzolan may be present in an amount ofabout 1% to about 25% bwoc. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount of thenatural pozzolan to include for a chosen application.

Metakaolin may be included in embodiments of the cement compositions ofthe present invention includes metakaolin. Generally, metakaolin is awhite pozzolan that may be prepared by heating kaolin clay, for example,to temperatures of about 600° to about 800° C. In some embodiments, themetakaolin may be present in the cement compositions of the presentinvention in an amount of about 0.1% to about 50% bwoc. In someembodiments, the metakaolin may be present in an amount of about 1% toabout 25% bwoc. One of ordinary skill in the art, with the benefit ofthis disclosure, will recognize the appropriate amount of the metakaolinto include for a chosen application.

Shale may be included in embodiments of the cement compositions of thepresent invention. Among other things, shale included in the cementcompositions may react with excess hydrated lime to form a suitablecementing material, for example, calcium silicate hydrate. A variety ofshales are suitable, including those comprising silicon, aluminum,calcium, and/or magnesium. An example of a suitable shale comprisesvitrified shale. Suitable examples of vitrified shale include, but arenot limited to, PRESSUR-SEAL FINE LCM material and PRESSUR-SEAL COARSELCM material, which are available from TXI Energy Services, Inc.,Houston, Tex. Generally, the shale may have any particle sizedistribution as desired for a particular application. In certainembodiments, the shale may have a particle size distribution of about 37micrometers to about 4,750 micrometers. Where present, the shale may beincluded in embodiments of the cement compositions of the presentinvention in an amount sufficient to provide, for example, the desiredcompressive strength, density, and/or cost. In some embodiments, theshale may be present in an amount of about 0.1% to about 50% bwoc. Insome embodiments, the shale may be present in an amount of about 1% toabout 25% bwoc. One of ordinary skill in the art, with the benefit ofthis disclosure, will recognize the appropriate amount of the shale toinclude for a chosen application.

Zeolite may be included in embodiments of the cement compositions of thepresent invention. Zeolites generally are porous alumino-silicateminerals that may be either a natural or synthetic material. Syntheticzeolites are based on the same type of structural cell as naturalzeolites, and may comprise aluminosilicate hydrates. As used herein, theterm “zeolite” refers to all natural and synthetic forms of zeolite.Examples of suitable zeolites are described in more detail in U.S. Pat.No. 7,445,669, the entire disclosure of which is incorporated herein byreference. An example of a suitable source of zeolite is available fromthe C2C Zeolite Corporation of Calgary, Canada. In some embodiments, thezeolite may be present in the cement compositions of the presentinvention in an amount of about 0.1% to about 50% bwoc. In certainembodiments, the zeolite may be present in an amount of about 1% toabout 25% bwoc. One of ordinary skill in the art, with the benefit ofthis disclosure, will recognize the appropriate amount of the zeolite toinclude for a chosen application.

Lime may be included in embodiments of the cement compositions of thepresent invention. In certain embodiments, the lime may be hydratedlime. In certain embodiments, the lime present in the cement compositionmay comprise, for example, a combination of unhydrated and hydratedlime. Where present, the lime may be present in the cement compositionsin an amount of about 0.1% to about 40% bwoc. In some embodiments, thelime may be present in the cement compositions in an amount of about 1%to about 20% bwoc. One of ordinary skill in the art, with the benefit ofthis disclosure, will recognize the appropriate amount of the lime toinclude for a chosen application.

As mentioned above, embodiments of the cement compositions of thepresent invention may be foamed, for example, further comprising a gasand a surfactant, in accordance with embodiments of the presentinvention. A foamed cement composition may be used, for example, whereit is desired for the cement composition to be lightweight. For example,a foamed cement composition of the present invention may comprisehydraulic cement, biowaste ash, a gas, a surfactant, and water. Othersuitable additives, such as those discussed herein, also may be includedin embodiments of the foamed cement compositions of the presentinvention as desired by those of ordinary skill in the art, with thebenefit of this disclosure.

The gas used in embodiments of the foamed cement compositions may be anygas suitable for foaming a cement composition, including, but notlimited to, air, nitrogen, or combinations thereof. Generally, the gasmay be present in embodiments of the foamed cement compositions of thepresent invention in an amount sufficient to form the desired foam. Incertain embodiments, the gas may be present in the foamed cementcompositions of the present invention in an amount of about 10% to about80% by volume of the composition.

Where foamed, embodiments of the cement compositions further maycomprise a surfactant. In some embodiments, the surfactant comprises afoaming and stabilizing surfactant composition. As used herein, a“foaming and stabilizing surfactant composition” refers to a compositionthat comprises one or more surfactants and, among other things, may beused to facilitate the foaming of a cement composition and also maystabilize the resultant foamed cement composition formed therewith. Anysuitable foaming and stabilizing surfactant composition may be used inthe cement compositions of the present invention. Suitable foaming andstabilizing surfactant compositions may include, but are not limited to:mixtures of an ammonium salt of an alkyl ether sulfate, acocoamidopropyl betaine surfactant, a cocoamidopropyl dimethylamineoxide surfactant, sodium chloride, and water; mixtures of an ammoniumsalt of an alkyl ether sulfate surfactant, a cocoamidopropylhydroxysultaine surfactant, a cocoamidopropyl dimethylamine oxidesurfactant, sodium chloride, and water; hydrolyzed keratin; mixtures ofan ethoxylated alcohol ether sulfate surfactant, an alkyl or alkeneamidopropyl betaine surfactant, and an alkyl or alkene dimethylamineoxide surfactant; aqueous solutions of an alpha-olefinic sulfonatesurfactant and a betaine surfactant; and combinations thereof. In onecertain embodiment, the foaming and stabilizing surfactant compositioncomprises a mixture of an ammonium salt of an alkyl ether sulfate, acocoamidopropyl betaine surfactant, a cocoamidopropyl dimethylamineoxide surfactant, sodium chloride, and water. A suitable example of sucha mixture is ZONESEAL® 2000 foaming additive, available from HalliburtonEnergy Services, Inc. Suitable foaming and stabilizing surfactantcompositions are described in U.S. Pat. Nos. 6,797,054, 6,547,871,6,367,550, 6,063,738, and 5,897,699, the entire disclosures of which areincorporated herein by reference. Generally, the surfactant may bepresent in the foamed cement compositions of the present invention in anamount sufficient to provide a suitable foam. In some embodiments, thesurfactant may be present in an amount of about 0.8% and about 5% byvolume of the water (“bvow”).

Other additives suitable for use in subterranean cementing operationsalso may be added to embodiments of the cement compositions, inaccordance with embodiments of the present invention. Examples of suchadditives include, but are not limited to, strength-retrogressionadditives, set accelerators, set retarders, weighting agents,lightweight additives, gas-generating additives, mechanical propertyenhancing additives, lost-circulation materials, filtration-controladditives, dispersants, a fluid loss control additive, defoaming agents,thixotropic additives, oil-swellable materials, water-swellablematerials, and combinations thereof. Specific examples of these, andother, additives include crystalline silica, amorphous silica, fumedsilica, salts, fibers, hydratable clays, calcined shale, microspheres,pumicite, diatomaceous earth, elastomers, resins, latex, combinationsthereof, and the like. A person having ordinary skill in the art, withthe benefit of this disclosure, will readily be able to determine thetype and amount of additive useful for a particular application anddesired result.

Embodiments of the cement compositions of the present invention may beused in a variety of subterranean applications where cement compositionsmay be used, including, but not limited to, primary cementing, remedialcementing, and drilling operations. An example of a method of thepresent invention may comprise introducing a cement compositionhydraulic cement, water, and biowaste ash into a subterranean formation;and allowing the cement composition to set in the subterraneanformation. As desired by one of ordinary skill in the art, with thebenefit of this disclosure, embodiments of the cement compositions ofthe present invention useful in this method may comprise any of theabove-listed additives, as well any of a variety of other additivessuitable for use in subterranean application. In example primarycementing embodiments, a cement composition may be introduced into aspace between a subterranean formation and a conduit (e.g., casing,expandable casing, liners, etc.) located in the subterranean formation.The cement composition may be allowed to set to form a hardened mass inthe space between the subterranean formation and the conduit. Inaddition, in example remedial cementing embodiments, a cementcomposition may used, for example, in squeeze cementing operations or inthe placement of cement plugs.

Another example of a method of the present invention is a method ofcementing that may comprise introducing a lightweight cement compositioninto a subterranean formation. Embodiments of the lightweight cementcomposition have a density of less than about 13 lb/gal and may comprisehydraulic cement, water, biowaste ash, and a lightweight additive (e.g.,bentonite, gilsonite, expanded perlite, microspheres, etc.). The methodfurther may comprise allowing the lightweight cement composition to setin the subterranean formation. As desired by one of ordinary skill inthe art, with the benefit of this disclosure, embodiments of thelightweight cement compositions of the present invention useful in thismethod may comprise any of the above-listed additives, as well any of avariety of other additives suitable for use in subterraneanapplications.

Another example of a method of the present invention is a method ofcementing that may comprise introducing a foamed cement composition thatcomprises hydraulic cement, water, biowaste ash, a gas, and a surfactantinto a subterranean formation. The method further may comprise allowingthe foamed cement composition to set in the subterranean formation. Asdesired by one of ordinary skill in the art, with the benefit of thisdisclosure, embodiments of the foamed cement compositions of the presentinvention useful in this method may comprise any of the above-listedadditives, as well any of a variety of other additives suitable for usein subterranean applications.

Another example of a method of the present invention is a method ofcementing a conduit (e.g., casing, expandable casing, liners, etc.)disposed in a subterranean formation. An example of such a method maycomprise introducing a cement composition comprising hydraulic cement,water, and biowaste ash into the annulus between the conduit and thesubterranean formation; and allowing the settable composition to set inthe annulus to form a hardened mass. Generally, in most instances, thehardened mass should fix the conduit in the formation. The methodfurther may comprise, for example, introducing the conduit into thesubterranean formation. As desired by one of ordinary skill in the art,with the benefit of this disclosure, embodiments of the cementcompositions of the present invention useful in this method may compriseany of the above-listed additives, as well any of a variety of otheradditives suitable for use in subterranean applications.

Another example of a method of the present invention is a method ofsealing a portion of a gravel pack or a portion of a subterraneanformation. An example of such a method may comprise introducing a cementcomposition comprising hydraulic cement, water, and biowaste ash intothe portion of the gravel pack or the portion of the subterraneanformation; and allowing the cement composition to form a hardened massin the portion. The portions of the subterranean formation may includepermeable portions of the formation and fractures (natural or otherwise)in the formation and other portions of the formation that may allow theundesired flow of fluid into, or from, the well bore. The portions ofthe gravel pack may include those portions of the gravel pack, whereinit is desired to prevent the undesired flow of fluids into, or from, thewell bore. Among other things, this method may allow the sealing of theportion of the gravel pack to prevent the undesired flow of fluidswithout requiring the gravel pack's removal. As desired by one ofordinary skill in the art, with the benefit of this disclosure,embodiments of the cement compositions of the present invention usefulin this method may comprise any of the above-listed additives, as wellany of a variety of other additives suitable for use in subterraneanapplications.

Another example of a method of the present invention is a method ofsealing voids located in a conduit (e.g., casing, expandable casings,liners, etc.) or in a cement sheath. Generally, the conduit may bedisposed in a wellbore, and the cement sheath may be located in theannulus between the conduit and a subterranean formation. An example ofsuch a method may comprise introducing a composition comprisinghydraulic cement, water, and biowaste ash into the void; and allowingthe cement composition to set to form a hardened mass in the void. Asdesired by one of ordinary skill in the art, with the benefit of thisdisclosure, embodiments of compositions of the present invention usefulin this method may comprise any of the above-listed additives, as wellany of a variety of other additives suitable for use in subterraneanapplications.

When sealing a void in a conduit, embodiments of the methods of thepresent invention, in some embodiments, further may comprise locatingthe void in the conduit; and isolating the void by defining a spacewithin the conduit in communication with the void, wherein the settablecomposition may be introduced into the void from the space. The void maybe isolated using any suitable technique and/or apparatus, includingbridge plugs, packers, and the like. The void in the conduit may belocated using any suitable technique. When sealing a void in the cementsheath, the methods of the present invention, in some embodiments,further may comprise locating the void in the cement sheath; producing aperforation in the conduit that intersects the void; and isolating thevoid by defining a space within the conduit in communication with thevoid via the perforation, wherein the cement composition is introducedinto the void via the perforation. The void in the conduit may belocated using any suitable technique. The perforation may be created inthe conduit using any suitable technique, for example, perforating guns.The void may be isolated using any suitable technique and/or apparatus,including bridge plugs, packers, and the like.

Another example of a method of the present invention is a method offorming a plug in a well bore. An example of such a method may includeintroducing a introducing a cement composition comprising hydrauliccement, water, and biowaste ash into the well bore at a location in thewell bore; and allowing the cement composition to set to form the plugin the well bore. The plug may be found, for example, when plugging andabandoning the well or to form a kickoff plug when changing thedirection of drilling the well bore. An example of changing thedirection of drilling a well bore may comprise introducing a cementcomposition comprising hydraulic cement, water, and biowaste ash intothe well bore at a location in the well bore wherein the direction ofdrilling is to be changed; allowing the cement composition to set toform a kickoff plug in the well bore; drilling a hole in the kickoffplug; and drilling of the well bore through the hole in the kickoffplug. As desired by one of ordinary skill in the art, with the benefitof this disclosure, embodiments of the cement compositions of thepresent invention useful in this method further may comprise any of theabove-listed additives, as well any of a variety of other additivessuitable for use in subterranean applications.

Generally, the drilling operation may continue, for example, in thedirection of the hole drilled through the kickoff plug. The well boreand hole in the kickoff plug may be drilled using any suitabletechnique, including rotary drilling, cable tool drilling, and the like.In some embodiments, one or more oriented directional drilling tools maybe placed adjacent to the kickoff plug. Suitable directional drillingtools include, but are not limited to, whip-stocks, bent sub-downholemotorized drill combinations, and the like. The direction drilling toolsthen may be used to drill the hole in the kickoff plug so that the holeis positioned in the desired direction. Optionally, the directionaldrilling tool may be removed from the well bore subsequent to drillingthe hole in the kickoff plug.

In accordance with embodiments of the present composition, the cementcompositions of the present invention may utilize a packing volumefraction suitable for a particular application as desired. As usedherein, the term “packing volume fraction” refers to the volume of theparticulate materials in a fluid divided by the total volume of thefluid. The size ranges of the preferred particulate materials may beselected, as well as their respective proportions, in order to provide amaximized packing volume fraction so that the fluid is in a hinderedsettling state. It is known that, in such a state, the particulatematerials behave “collectively” like a porous solid material. Thehindered settling state is believed to correspond, in practice, to amuch higher solid material concentration in the fluid than that presentin the some traditional cement compositions.

Embodiments of the present invention may include a combination of atleast three features to obtain a maximum packing volume. One is the useof at least three particulate materials wherein the alt least threeparticulate materials are in size ranges “disjointed” from one another.In some embodiments, each of the three particulate materials may includea different particle size selected from the following ranges: about 7 nmto about 50 nm, about 0.05 microns to about 0.5 microns, 0.5 microns toabout 10 microns, about 10 microns to about 20 microns, about 20 micronsto about 200 microns, about 200 microns to about 800 microns, andgreater than about 1 millimeter. For example, a first particulatematerial may include particles sized from about 7 nm to about 50 nm, asecond particulate material may include particles sized from about 0.05microns to about 0.5 microns, and a third particulate material mayinclude particles sized from about 10 microns to about 20 microns.Another aspect of embodiments of the present invention presentembodiments may include a choice of the proportions of the threeparticulate materials in relation to the mixing, such that the fluid,when mixed, is in a hindered settling state. Another feature may includethe choice of the proportions of the three particulate materials betweeneach other, and according to their respective size ranges, such that themaximum packing volume fraction is at least substantially achieved forthe sum total of all particulate materials in the fluid system. Inaccordance with embodiments of the present invention, biowaste ash maybe used to obtain a maximum packing volume fraction. By way of example,biowaste ash having a particle size of about 7 nm to about 1 millimetermay be used to obtain a maximum packing volume fraction. Packing volumefraction is described in further detail in U.S. Pat. No. 5,518,996 andU.S. Pat. No. 7,213,646, the entire disclosures of which areincorporated herein by reference.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered ormodified and all such variations are considered within the scope andspirit of the present invention. While compositions and methods aredescribed in terms of “comprising,” “containing,” or “including” variouscomponents or steps, the compositions and methods can also “consistessentially” of or “consist of” the various components and steps.Whenever a numerical range with a lower limit and an upper limit isdisclosed, any number and any included range falling within the range isspecifically disclosed. In particular, every range of values (of theform, “about a to about b,” or, equivalently, “from approximately a tob,” or, equivalently, “from approximately a-b”) disclosed herein is tobe understood to set forth every number and range encompassed within thebroader range of values. Also, the terms in the claims have their plain,ordinary meaning unless otherwise explicitly and clearly defined by thepatentee.

What is claimed is:
 1. A subterranean formation cementing compositioncomprising: Portland cement; water in an amount sufficient to form apumpable slurry; biowaste ash, wherein the biowaste ash does not includefly ash or rice hull ash, wherein the biowaste ash has been burned in arange of from about 2 hours to about 8 hours at a temperature in a rangeof from about 500° C. to about 700° C., and wherein the biowaste ash ispresent in the subterranean formation cement composition in an amount ofabout 1% to about 25% by weight of the Portland cement; at least onecomponent selected from the group consisting of cement kiln dust, anatural pozzolan, metakaolin, shale, slag, zeolite, and combinationsthereof; and at least one additive selected from the group consisting ofa strength-retrogression additive, a set accelerator, a set retarder, aweighting agent, a lightweight additive, a gas-generating additive, amechanical-property-enhancing additive, a lost-circulation material, afiltration-control additive, a dispersant, a fluid loss controladditive, a defoaming agent, a foaming agent, a thixotropic additive, anoil-swellable material, a water-swellable material, and combinationsthereof; wherein the subterranean formation cement composition has adensity of less than about 13 pounds per gallon.
 2. The composition ofclaim 1 wherein the biowaste ash comprises at least one biowaste ashselected from the group consisting of, municipal waste ash, waste-watertreatment waste ash, animal waste ash, non-human, non-animal industrialwaste ash, and combinations thereof.
 3. The composition of claim 1wherein the biowaste ash comprises agricultural waste ash.
 4. Thecomposition of claim 1 wherein the biowaste ash comprises at least oneagricultural waste ash selected from the group consisting of wood ash,tree leave ash, corn cob ash, cane ash, bagasse ash, grain ash, grainrelated by-product ash, orchard ash, vine trimming ash, grass ash, strawash, ground nut shell ash, legume ash, and combinations thereof.
 5. Thecomposition of claim 1 wherein the biowaste ash comprises municipalwaste ash.
 6. The composition of claim 1 wherein the biowaste ashcomprises municipal solid waste ash.
 7. The composition of claim 1wherein the subterranean formation cement composition further comprisesat least one additive selected from the group consisting of acrystalline silica, amorphous silica, fumed silica, a salt, fiber,hydratable clay, calcined shale, a microsphere, pumicite, diatomaceousearth, an elastomer, a resin, latex, and combinations thereof.
 8. Thecomposition of claim 1 wherein the subterranean foil ration cementcomposition is a foamed cement composition further comprising a gas anda surfactant.
 9. The composition of claim 1 further comprisingmaximizing a packing volume in the subterranean formation cementcomposition using at least one particulate material with a particle sizeof about 7 nanometers to about 1 millimeter, wherein the at least oneparticulate material comprises the biowaste ash.
 10. A cementcomposition comprising: hydraulic cement comprising at least one cementselected from the group consisting of a Portland cement, a pozzolanacement, a gypsum cement, a high-alumina-content cement, a slag cement, asilica cement, and combinations thereof, and wherein the hydrauliccement is present in the cement composition an amount of about 1% toabout 75% by weight of the hydraulic cement; water in an amountsufficient to form a pumpable slurry, wherein the water is present in anamount in a range of from about 40% to about 200% by weight of thehydraulic cement; biowaste ash comprising municipal waste ash, whereinthe biowaste ash does not include fly ash or rice hull ash, wherein thebiowaste ash has been burned in a range of from about 2 hours to about 8hours at a temperature in a range of from about 500° C. to about 700°C., and wherein the biowaste ash is present in the cement composition inan amount of about 1% to about 25% by weight of the hydraulic cement;and at least one additive selected from the group consisting of cementkiln dust, a natural pozzalon, metakaolin, shale, slag, zeolite, andcombinations thereof; wherein the cement composition has a density ofabout 8 pounds per gallon to about 17 pounds per gallon.
 11. Thecomposition of claim 10 wherein the cement composition further comprisesat least one additive selected from the group consisting of astrength-retrogression additive, a set accelerator, a set retarder, aweighting agent, a lightweight additive, a gas-generating additive, amechanical-property-enhancing additive, a lost-circulation material, afiltration-control additive, a dispersant, a fluid loss controladditive, a defoaming agent, a foaming agent, a thixotropic additive, anoil-swellable material, a water-swellable material, and combinationsthereof.
 12. The composition of claim 10 wherein the cement compositionfurther comprises at least one additive selected from the groupconsisting of a crystalline silica, amorphous silica, fumed silica, asalt, fiber, hydratable clay, a microsphere, pumicite, diatomaceousearth, an elastomer, a resin, latex, combinations thereof.
 13. Thecomposition of claim 10 wherein the cement composition is a foamedcement composition further comprising a gas and a surfactant.
 14. Thecomposition of claim 10 further comprising maximizing a packing volumein the cement composition using at least one particulate material with aparticle size of about 7 nanometers to about 1 millimeter, wherein theat least one particulate material comprises the biowaste ash.
 15. Thecomposition of claim 10 wherein the natural pozzolan is pumicite.
 16. Acomposition comprising: cement kiln dust; water in an amount in a rangeof from about 40% to about 200% by weight of the cement kiln dust; andmunicipal solid waste ash, wherein the municipal solid waste ash doesnot include fly ash or rice hull ash, wherein the municipal solid wasteash has been burned in a range of from about 3 hours to about 6 hours ata temperature in a range of from about 500° C. to about 700° C., andwherein the municipal solid waste ash is present in the composition inan amount of about 1% to about 25% by weight of the cement kiln dust;wherein the composition has a density of less than about 13 pounds pergallon.
 17. The composition of claim 16 wherein the composition furthercomprises at least one component selected from the group consisting of,a natural pozzolan, metakaolin, shale, slag, zeolite, and combinationsthereof.
 18. The composition of claim 16 wherein the composition furthercomprises at least one additive selected from the group consisting of acrystalline silica, amorphous silica, fumed silica, a salt, fiber,hydratable clay, calcined shale, a microsphere, pumicite, diatomaceousearth, an elastomer, a resin, latex, and combinations thereof.
 19. Thecomposition of claim 16 wherein the composition further comprises atleast one additive selected from the group consisting of astrength-retrogression additive, a set accelerator, a set retarder, aweighting agent, a lightweight additive, a gas-generating additive, amechanical-property-enhancing additive, a lost-circulation material, afiltration-control additive, a dispersant, a fluid loss controladditive, a defoaming agent, a foaming agent, a thixotropic additive, anoil-swellable material, a water-swellable material, and combinationsthereof.